1. Field of the Invention
The present invention relates to a Fe based hard magnetic alloy, especially to a Fe based hard magnetic alloy having a wide super-cooled liquid region, bearing a hard magnetism at room temperature after a heat treatment and being able to form into a bulky permanent magnet molded member.
2. Description of the Related Art
Some of conventional alloys composed of a plurality of elements have a wide temperature range to remain in a super-cooled liquid state prior to crystallization, so that these alloys can form glassy alloys. It is known in the art that this kind of glassy alloys can be molded into a bulky alloy far more thicker than thin films of amorphous alloys produced by a conventional melt quenching method.
While Fe--P--C amorphous alloys first produced in 1960's, (Fe, Co, Ni)--P--B alloys and (Fe, Co, Ni)--Si--B alloys first produced in 1970's, and (Fe, Co, Ni)--M (Zr, Hf, Nb) alloys and (Fe, Co, Ni)--M (Zr, Hf, Nb)--B alloys first produced in 1980's have been known as examples of amorphous alloy thin films, all of these alloys are inevitably produced by quenching at a cooling rate of the order of 10.sup.5 K/s, thereby films with a thickness of 50 .mu.m or less were produced.
Accordingly, production of thick and bulky bonded magnets have been devised. Since these bonded magnets were formed, however, by a compression molding or injection molding after mixing a magnetic powder, produced by quenching a molten liquid mainly composed of Nd.sub.2 Fe.sub.14 B phase, and an exchange spring magnetic powder of Fe.sub.3 B--Nd.sub.2 Fe.sub.14 B.sub.1 alloys with a binder comprising a rubber or plastic, their magnetic properties became poor besides having a weak strength as materials. In the glassy metal alloys, on the other hand, an alloy with a thickness of several mm can be formed. Alloys with compositions of Ln--Al--TM, Mg--Ln--TM and Zr--Al--TM (wherein Ln denotes a rare earth element while TM denotes a transition metal) were discovered in the years of 1988 to 1991 as these sort of glassy alloys described above.
However, since these conventional glassy metal alloys did not exhibit any magnetism at room temperature, industrial applications as hard magnetic materials were largely restricted.
Therefore, R & D of glassy metal alloys capable of obtaining thick bulky alloys with hard magnetism at room temperature have been carried out.
The temperature interval .DELTA. T.sub.x in the super-cooled liquid area, that is, an interval between crystallization temperature (T.sub.x) and glass transition temperature (T.sub.g), or a numerical value of (T.sub.x -T.sub.g), is usually small in alloys with a variety of composition even when a state of super-cooled liquid area exists in the alloy. By considering the fact that conventional alloys have actually a poor ability for forming glassy metals and are of little practical values, the presence of alloys having a wide temperature range in the super-cooled liquid region and being capable of forming a glassy alloy with a single amorphous phase by cooling can overcome the limitation in thickness of thin films in the conventional amorphous alloys. In addition, If the amorphous single phase can be obtained, the crystal texture can be fine and uniform after heat treatment. It is largely noticeable from metallurgical interests. And discovery of glassy metal alloys that exhibit ferromagnetism at room temperature would be a key problem whether the alloys could be developed as industrial materials or not.